Core Data Structures and Recursion

Solve simple problems using recursion to understand the call stack (e.g., factorial, string reversal).

Implement a basic singly linked list with insertion, deletion, and traversal operations.

Use Java's Deque interface to implement stack (LIFO) and queue (FIFO) behaviors.

Solve problems using a HashMap for frequency counting and quick lookups.

Implement depth-first binary tree traversals (inorder, preorder, postorder) using recursion.

Implement level-order traversal of a binary tree using a queue (BFS).